Electric fuel pump riddle....???

[Aussie_70_Sport_Fury]

From the WTF Files!!!!
Q. What is it that goes down the hotter it gets???
A. My bloody fuel pressure!!! :-x :-x :-x :-x

Engine has a 160F thermostat, fan shroud is missing, I know while stationary this is an issue but at 50mph its not a problem.
I had a Holley electric fuel pump installed, with a regulator that was supplied with it. installer even fitted an LPG cut off relay system in the event of fire or crash.
Now when the car gets hot, the car stalls after its been sitting hot i.e. stopping at a servo and filling up...I drive a short distance and the engine just dies...after this happened a couple of times I checked the carby and it was dripping fuel as though it had way too much line pressure? You need to crank and crank and crank the motor to get it to fire again, without touching the throttle.
As the regulator didn't have a gauge, Amazon.com fixed that so I can see for sure the fuel pressure going past 10psi....or so I thought?????
I fitted a phenolic spacer under the carby to stop heat soak, now has a tiny air cleaner to close hood!!
This lessoned the heat soak into the carby a fair bit and the boiling burbling noise in the float bowls stopped.


Now....when I first run the car...I see 6psi line pressure...pretty happy...car is just warming up here in this pic.






Location of the regulator in the engine bay.






Engine is warmed up, thermostat opened, car idling at 800rpm easily (race carby has no choke fitted) line pressure has already dropped 1psi..?






Car has been driven 15mins, parked for 10mins and heat soaked a little, temp gauge shows 200F and fuel line pressure has fallen by 50% to 3psi??? (Oil pressure gauge line was leaking so its not connected)








Car driven back to parking spot, engine now over 215+ F and car stumbling a little off idle at lights...usual ethanol boiling issue I think. Line pressure now closer to 2psi?? WTF is causing this to happen!!!!

 

[68-300]

I see you have a fluid filled fuel pressure gauge, they can give a false reading when they are hot, try cooling the gauge (with some ice) when the engine is hot and the pressure is down and see what happens with the pressure.

 

[Badvert65]

Where is your fuel pump located? Is there any possibility it is getting heat soaked? I have had this happen to me. My pump is located on the inside frame just ahead of the right rear wheel. Wasn't a problem until I got Flow Master mufflers. Those things get REALLY hot. No issues if moving, but if I stopped, even for a moment, pressure dropped off to nothing. I moved the pump to outside the frame and wrapped it with heat shielding. So far, so good.

 

[Mopars & Missiles]

I see you have a fluid filled fuel pressure gauge, they can give a false reading when they are hot,.....

EXACTLY the problem.

A fluid filled gauge (or sealed gauge) has a reference pressure equal to the internal (sealed) pressure of the gauge. As it gets hotter, this internal reference pressure increases slightly. The gauge measures the PRESSURE DIFFERENTIAL between the internal reference pressure and the input (gas) pressure. So, as temperature increases, you will see a slight DECREASE in measured pressure on the gauge which is actually not accurate to the actual gas pressure. Your best accuracy with this type of gauge will be when the engine is first started before it becomes heat soaked. The advantage of this fluid filled gauge is that the fluid dampens the needle movement and it displays a more steady or constant reading than the unfilled type gauge.

An unfilled gauge (or unsealed gauge) always has an outside reference pressure from the surrounding atmosphere since it is a vented type and is more accurate when hot, but because this type of gauge cannot be fluid filled the needle indicator will bounce more than a fluid filled type.

 

[detmatt]

You do need a shroud. I don't care how fast you're going, it'll help. How far is your fan from the radiator?

 

[saylor]

for me when i was going thru this hell, i ended up pulling the mech fuel pump and going electric, and that didnt fix it. i next ditched the glass fuel filter up by the carb and ran metal line from the feed down by the frame @ the mech FP location all the way to the carb with one long piece of brake line from vatozone.

next thing i did was got my timing dialed in.

its not super hot here yet - so we will see how it goes this summer, but right now, all day @185-190, even sitting at a light. no stumble. easy starting.

shut it off let it get soak up to 210-220 - starts right up and goes to 185-190 almost immediately.

there is a chance that a 160 thermostat is too small. you may want to step up to a 180 - 185 tstat.

- saylor

 

[CanCritter]

A.shroud..put it back on to start..why folks run without them simply amazes me
B. fuel lines...enshure their clear of heat sources or gas will perculate giving you a foulded filter type symptoms
C.regulator...not shure about carbs but on efi setups fuel reg is on return line to tank after TBI/carb..may wana enshure its where its susposed to be..
D timeing right?

that's it for me....